Composition and method for controlling the wettability of surfaces

ABSTRACT

The present invention relates to a composition comprising hedgehog shaped particles, at least one binder, and at least one hydrophobizing agent and/or at least one hydrophilizing agent, a method for controlling the wettability of substrate surfaces using these compositions, as well as a material comprising these compositions.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation of U.S. application Ser. No. 14/370,867, filedJul. 7, 2014, which is the U.S. National phase of PCT Application No.PCT/EP2013/052128, filed Feb. 4, 2013, which claims priority to EuropeanApplication No. 12154687.3, filed Feb. 9, 2012 and U.S. ProvisionalApplication No. 61/599,021, filed Feb. 15, 2012, the contents of whichare hereby incorporated by reference.

The present invention relates to a composition for controlling thewettability of surfaces, to coating formulations comprising the same, toa method for controlling the wettability of surfaces using thiscomposition or a corresponding coating formulation, and their uses.

There is a continuous interest in providing tailor-made properties tomaterials by controlling their surface structure properties. Onewell-known example therefor is the lotus effect referring to very highwater repellence (superhydrophobicity) of certain plant leaves, whereindirt particles are picked up by water droplets due to a complex micro-and nanoscopic architecture of the surface, which minimizes adhesion.

Due to their high surface tension, water droplets tend to minimize theirsurface trying to achieve a spherical shape. On contact with a surface,adhesion forces result in wetting of the surface.

In nature, the self-cleaning properties are due to a hydrophobicwater-repellent double structure of the leaf surface formed out of acharacteristic epidermis and the covering waxes. The epidermis of thelotus plant has papillae with 10 to 20 μm in height and 10 to 15 μm inwidth on which the so-called epicuticular waxes are imposed. Thesesuperimposed waxes are hydrophobic and form the second layer of thedouble structure, enabling the contact area and the adhesion forcebetween surface and droplet to be significantly reduced resulting in aself-cleaning process.

The surface free energy of a wax is relatively low and a drop of wateron a smooth surface of this wax material would show a contact angle >90°but probably <120°. The structural impact derives from the exposed tipsand edges of the papillae which minimize the solid/liquid contact area,resulting in a dominance of the cohesive forces of the liquid dropstriving for a spherical shape (Cassie and Baxter, Trans. Faraday Soc.1944, 40, 546).

As a result, a complete repellence can be observed with a contact angleapproaching 180° and the droplet rolls off the surface leaving no trace.A contrasting phenomenon is also known when the intrinsic contact angleis relatively low, e.g. <45°. A designed textured surface can act toenhance the wetting, the apparent contact angle becomes 0° and thephenomenon is called super-wettability (Wenzel, Ind. Eng. Chem. 1936,28, 988).

Especially the lotus effect was intensively studied from a theoreticalpoint of view (cf. e.g. Narhe et al., Water Condensation on asuper-hydrophobic spike surface, Europhys. Lett. 2006, 75(1), 98-104;Wier et al., Langmuir 2006, 22, 2433-2436; Gao et al., Langmuir 2007,23, 3762-3765) as well as with respect to its practical use in technicalapplications, such as treatments, coatings, paints, roof tiles, fabricsand other surfaces that can stay dry and clean themselves in the sameway as the lotus leaf.

In this respect, the required surface structure was obtained by rathercomplicated techniques modifying the surface itself, e.g. by applying248 nm KrF excimer-laser irradiation in vacuum on PET foils (Heitz etal., Dendritic Surface Structures on Excimer-Laser Irradiated PET Foils;Appl. Phys. A 1993, 56, 329-333), plasmapolymerization on thesubstrates, argon plasma etching, silanization of silicone wafers, etc.(Chen et. al., Ultrahydrophobic and Ultralyophobic Surfaces: SomeComments and Examples; Langmuir 1999, 15, 3395-3399; Öner et al.,Ultrahydrophobic surfaces. Effects of Topography Length Scales onWettability, Langmuir 2000, 16, 7777-7782); the preparation of complexand oriented ZnO nanostructures using controlled seeded growth andcitrate anions that selectively adsorb on ZnO basal planes as thestructure directing agent (Tian et al., Complex and oriented ZnOnanostructures, nature materials 2003, 2, 821-826).

In industrial applications, however, problems arise from mechanicalinstability, as artificial surfaces, unlike plant structures, are notself-renewing, and there is still need for further innovative materialproviding a possibility to control the surface properties of differentmaterials.

Furthermore, there is a need for readily applicable formulations, i.e.formulations which may be directly applied onto the substrate surface ina readily operable and available manner.

In this respect, there were some approaches to provide substrates withthe Lotus effect by coating formulations. Thus, e.g. EP 1 144 332 B1discloses coating formulations consisting of a dispersion of a bindingagent, including at least one hydrophobic resin, resin fabricatedmaterial and/or wax, filler and optionally usual additives, wherein thecontained filler has an at least bimodal particle size distribution,whereby one particle size region (A) has a mean particle diameter of atleast 5 μm and the other particle size region (B) has a particlediameter of not greater than 3 μm and the weight ratio of the particlesof the first particle size region (A) to the particles of the lastparticle size region (B) amounts to 0.01:1 to 12:1, and wherein thehydrophilic characteristics of the components of the dispersion arechosen in such a way that the initial static contact angle is greaterthan 130° after three minutes of equilibration.

However, none of the mentioned technical solutions directed to the lotuseffect do address a method for controlling wettability by certainformulations, i.e. to control wettability in a scale ofsuperhydrophobicity to superwettability as desired.

It has now been found that hedgehog shaped particles may beadvantageously used in surface modifying applications by embedding theminto a coating layer using binders in such a way that the surface undera SEM microscope still shows exposed spikes and tips. If in combinationwith such hedgehog shaped particles, and coating formulation, ahydrophobization and/or hydrophilization agent is added and/or appliedon top in a thin layer (monolayer to multilayer), the wettability can becontrolled accurately from extremely hydrophobic to extremelyhydrophilic.

It has also been found that mixtures of pre-hydrophobized andpre-hydrophilized hedgehog shaped particles may be advantageously used.When the amount of hydrophobized particles surpasses the percolationthreshold the system may have a lotus effect like roll-off of dropletswhile still maintaining hydrophilic sites which collect water byadsorption and allow for droplet growth to a given size where gravityforces overcome the adhesion forces.

Thus, the present invention relates to a composition comprising

hedgehog shaped particles,

at least one binder, and

at least one hydrophobizing agent and/or at least one hydrophilizingagent.

“Hedgehog shaped particles” in the context of the present inventionmeans particles having the shape of a hedgehog, which means that theparticles are shaped such that spikes and/or tips are essentiallyradially extending from a core. This shape may be due to a correspondingcrystal growth or may be achieved by moulding or templating theparticles by techniques known to the person skilled in the art.

It is also possible that the hedgehog shape is due to the agglomerationor formation of clusters of needle like crystals to form a hedgehog likeshape.

Generally, the hedgehog shaped particles may be composed of any suitablematerial. In a preferred embodiment, the hedgehog shaped particles arecomposed of a material selected from the group comprising calciumcarbonate containing material, especially precipitated calciumcarbonate, natural calcium carbonate containing material, satin white,and mixtures thereof.

If the hedgehog shaped particles are composed of precipitated calciumcarbonate (PCC), it is especially preferred that the hedgehog shapedparticles are composed of a material comprising aragonitic, calcitic,vateritic precipitated calcium carbonate, or mixtures thereof.

Particularly useful in the present invention are hedgehog shapedparticles being composed of a material comprising clusters and/oraggregates of scalenohedral or orthorhombic-dipyramidal precipitatedcalcium carbonate crystals.

PCC which may be especially useful in the present invention is obtainedby a process described in unpublished European patent application No. 10188 840.2, wherein low quality carbonates can be transformed into verypure precipitated calcium carbonates with an excellent brightness anddefined structure.

This is achieved by

-   a) providing and calcining calcium carbonate comprising material;-   b) slaking the reaction product obtained from step a) with an    aqueous ammonium chloride solution;-   c) separating insoluble components from the calcium chloride    solution obtained from step b);-   d) carbonating the calcium chloride solution obtained from step c);-   e) separating the precipitated calcium carbonate obtained from step    d).

The special feature of this PCC production process is the combination ofcalcium oxide obtained from step a) with an aqueous solution of ammoniumchloride in step b), resulting in the formation of highly solublecalcium chloride, whereas undesired impurities initially contained inthe calcium carbonate feed material remain insoluble or are at leastless soluble than calcium chloride in the resulting alkaline ammoniacmedium allowing a separation.

Furthermore, due to the use of seed crystals or other structuremodifying chemicals to the calcium chloride-solution obtained from stepc) before precipitation, it is possible to ensure that the precipitationproducts crystallize in a certain shape and particle size range.

Furthermore, PCC which may be advantageously used in the composition ofthe present invention may be obtained by a process described in EP 2 371766, namely a process for preparing a precipitated calcium carbonateproduct comprising the steps of:

-   (a) preparing an aqueous suspension of precipitated calcium    carbonate seeds by carbonating a suspension of Ca(OH)₂ in the    presence of 0.005 to 0.030 moles of strontium, in the form of    Sr(OH)₂, per mole of Ca(OH)₂ prior to or during carbonation; and-   (b) forming an aqueous suspension of a precipitated calcium    carbonate product by carbonating a slurry of Ca(OH)₂ in the presence    of 0.5 to 5% by dry weight of the precipitated calcium carbonate    seeds,    wherein the precipitated calcium carbonate seeds have a d₅₀ that is    less than the d₅₀ of the precipitated calcium carbonate product and    the precipitated calcium carbonate seeds have an aragonitic    polymorph content greater than or equal to the precipitated calcium    carbonate product.

There are however also other techniques to obtain hedgehog shapedparticles of PCC useful in the present invention, which are well-knownin the art, e.g. from L. Zhu et al., Journal of Solid State Chemistry179 (2006), 1247-1252.

The hedgehog shaped particles used in the present invention preferablyhave a BET specific surface area of from 1 to 50 m²/g, especiallypreferably 2 to 40 m²/g, more preferably 11 to 35 m²/g, most preferably15 to 20 m²/g, measured using nitrogen and the BET method according toISO 9277.

In a preferred embodiment the hedgehog shaped particles have a weightmedian particle diameter d₅₀ of from 1 μm to 50 μm, preferably of from 2μm to 40 μm, more preferably of from 3 μm to 30 μm determined by thesedimentation method using a Sedigraph™ 5100 device from the companyMicromeritics, USA. The measurement was performed in an aqueous solutionof 0.1 wt-% Na₄P₂O₇. The samples were dispersed using a high-speedstirrer and ultrasound.

Hydrophobizing agents, as well as hydrophilizing agents, which may beadvantageously used in the context of the present invention are thosewell-known in the art of coatings, paints, etc.

In an especially preferred embodiment, the hydrophobizing agent isselected from the group comprising fatty acids, such as stearic acid,palmitic acid, and their salts; alkylketene dimer; polyacrylamideresins; silicone resins, polysiloxanes, preferably polysiloxane modifiedwith functional silicone resin, and mixtures thereof.

Especially preferred hydrophilizing agents are selected from the groupcomprising polyacrylic acids, salts of 1-hydroxyethane-1,1-diphosphonicacid, preferably alkali metal salts thereof, more preferably potassiumsalts thereof; and chelates of 1-hydroxyethane-1,1-diphosphonic acid,preferably aluminium hydroxide chelates thereof, more preferablyaluminium hydroxide/1-hydroxyethane-1,1-diphosphonic acid chelateshaving a weight ratio of 1:5, and mixtures thereof.

The amounts of the at least one hydrophobizing agent and/or at least onehydrophilizing agents also depend on the desired wettability effect, andwill be readily determinable by corresponding tests with the specificagents used.

Typically, the total amount of the at least one hydrophobizing agentand/or at least one hydrophilizing agents will be from 0.1 to 10 wt %,preferably 0.2 to 5 wt %, more preferably 0.3 to 2.4 wt %, mostpreferably 0.4 to 1.9 wt %, especially 0.5 to 1.5 wt %, based on theweight of the hedgehog shaped particles.

The binder used in the present invention may be any conventional binderused in the field of paper and board coating, paints and coatings, andimpregnations. It is preferably selected from the group comprising latexbinders, hybrid binder systems, preferably homopolymers or copolymers ofacrylic and/or methacrylic acids, itaconic acid; and acid esters, suchas e.g. ethylacrylate, butyl acrylate; styrene, unsubstituted orsubstituted vinyl chloride, vinyl acetate, ethylene, butadiene,acrylamides and acrylonitriles; silicone resins, water dilutable alkydresins, acrylic/alkyd resin combinations, polyvinyl alcohol, naturaloils, preferably linseed oil, and mixtures thereof.

If binders are used having hydrophobic and/or hydrophilic properties,the binders may act as the at least one hydrophobizing agent and/or theat least one hydrophilizing agent, i.e. binder and at least onehydrophobizing agent and/or at least one hydrophilizing agent areidentical compounds.

Depending on the substrate and the nature of the hedgehog shapedparticles as well as the hydrophobizing and/or hydrophilizing agents, aproper amount of the binder is one ensuring the binding of the differentcomponents with each other and with the substrate to be coated with thecomposition without influencing their properties.

Typically, the binder is present in an amount of up to 250 wt %,preferably up to 200 wt %, more preferably up to 150 wt %, mostpreferably up to 120 wt %, and especially preferably is present in anamount of from 1 to 50 wt %, preferably from 3 to 25 wt %, morepreferably from 5 to 20 wt %, especially preferably from 10 to 15 wt %,based on the weight of the hedgehog shaped particles.

The composition may be provided in different forms.

In one embodiment of the invention, the hedgehog shaped particles arecombined with the at least one hydrophobizing agent and/or at least onehydrophilizing agent, and the binder.

In another preferred embodiment, the hedgehog shaped particles arepre-treated with the at least one hydrophobizing agent and/or at leastone hydrophilizing agent. Subsequently, the hedgehog shaped particlespre-treated with at least one hydrophobizing agent and/or at least onehydrophilizing agent, or mixtures thereof, are mixed with the binder,wherein, optionally, further at least one hydrophobizing agent and/or atleast one hydrophilizing agent, which may be the same as, or differentfrom the agent used in the pre-treatment may be additionally added.

The composition also includes embodiments, where the hedgehog shapedparticles are first mixed with the binder and subsequently combined withthe at least one hydrophobizing agent and/or at least one hydrophilizingagent.

The composition according to the present invention may be provided inthe form of a coating formulation, wherein the composition, may bedissolved or dispersed in a suitable medium, e.g. a medium selected fromthe group comprising water, alcohol ethers, alcohols, aliphatichydrocarbons, esters, and mixtures thereof.

In some embodiments, it may also be advantageous to use mixtures ofsolvents, such as mixtures of water with other solvents as e.g. thosementioned above, optionally in combination with conventional additives,such as coalescence agents, e.g. Texanol®; defoamers, preferably mineraloil and/or silicone based defoamers; rheology modifiers, preferablycellulosic ethers, layer silicates, associative and non-associativeacrylics, or polyurethanes.

It is however also possible to use the composition as such, especiallyif one or more of the components are liquids and are present in asufficient amount to distribute it evenly on the substrate surface, e.g.if linseed oil is used as a binder.

Furthermore, a coating formulation comprising the composition accordingto the invention may comprise common additives, such as dispersingagents, siliconizing agents, thickeners, rheology modifiers,anti-settling agents, defoamers, antioxidants, bluing agents,surfactants, crosslinkers, flame retardants, catalysts, pH buffers,fillers, dyes, pigments, optical brightners, waxes, coalescence agents,biocides etc. in free or encapsulated form, e.g. in the form of slowrelease preparations such as those described in EP 2 168 572, orunpublished patent application No. 11 188 597.6, and mixtures thereof.

As the compositions according to the invention allow for the control ofthe wettability of surfaces, a corresponding method for the control ofthe wettability of surfaces is a further aspect of the presentinvention.

This is achieved by coating the above described compositions accordingto the invention onto the substrate.

For this purpose, the composition according to the present invention ispreferably provided in the form of a coating formulation as describedabove.

Thus, the substrate may be coated with a coating formulation of thecomposition comprising the hedgehog shaped particles, the at least onebinder, and the at least one hydrophobizing agent and/or at least onehydrophilizing agent.

The substrate may also be coated with a coating formulation of thecomposition comprising the hedgehog shaped particles being pre-treatedwith the at least one hydrophobizing agent and/or at least onehydrophilizing agent and mixed with the at least one binder, wherein,optionally, further at least one hydrophobizing agent and/or at leastone hydrophilizing agent, which may be the same as or different from theagent used in the pre-treatment may be additionally added, before thecoating formulation is applied to the substrate.

In a further embodiment, the composition may be applied in the form of acoating formulation comprising the hedgehog shaped particles and thebinder, which are coated onto the substrate first, whereas the at leastone hydrophobizing and/or hydrophilizing agent is applied on top of thecoating of hedgehog shaped particles and binder as one or severalpost-layers, such that the composition of the present invention isformed directly on the substrate.

Such post layers of at least one hydrophobizing and/or hydrophilizingagent may generally be applied with respect to any one of theabove-described coating formulations, i.e. may also be additionallyapplied onto a coating of mixtures of the hedgehog shaped particles, theat least one hydrophobizing and/or hydrophilizing agent, and the binder,as well as mixtures of hedgehog shaped particles pre-treated with atleast one hydrophobizing agent and/or at least one hydrophilizing agent,or mixtures thereof, and the binder, wherein, optionally, further atleast one hydrophobizing agent and/or at least one hydrophilizing agent,which may be the same as or different from the agent used in thepre-treatment, or the post-layer, may be additionally added.

It may also be advantageous to apply post-layers of further ingredientsand additives onto the coatings described above, preferably materialsselected from the group comprising resins, silicones, and tetrafluorocompounds.

The coating as well as the application of post-layers may be carried outby conventional techniques well-known in the art and suitable for therespective substrates, e.g. by spraying, immersion coating, rolling orbrushing, wherein the application of the post-layer advantageously iscarried out in the form of a corresponding solution or dispersion of theat least one hydrophobizing agent and/or at least one hydrophilizingagent or other ingredient or additive, when the coating has alreadydried.

Coatings as well as post-layers of the same or different compositionsand ingredients may be applied once or several times.

The substrate may generally be any substrate, e.g. a substrate selectedfrom the group comprising paper, board, wall-paper, wood, woodcomposites such as flake board, plastics, foil, concrete, coated oruncoated rendering, plaster, metals, ceramics, stone, brickstone, glass,etc.

The coated substrate is advantageously dried, be it at room temperatureor elevated temperatures depending on the solvent, which is optionallyused.

By a corresponding selection of the hydrophobizing, hydrophilizingagents or mixtures thereof, the substrates can be made superhydrophobicproviding a lotus effect to the substrate surface, or superhydrophilicproviding super-wettability, and hydrophobicity/hydrophilicity may becontrolled as desired by a corresponding mixture.

Thus, mixtures of pre-hydrophobized and pre-hydrophilized hedgehogshaped particles may be advantageously used, wherein, e.g. firstdiscrete hydrophobic sites are formed combining to hydrophobic domainsin a hydrophilic environment.

When the amount of hydrophobized particles exceeds the percolationthreshold the system may have a lotus effect like roll-off of dropletswhile still maintaining hydrophilic sites which collect water byadsorption and allow for droplet growth to a given size where gravityforces overcome the adhesion forces.

By a suitable selection and mixture of hydrophobizing agents andhydrophilizing agents, contact angles may be achieved which are close to0° up to 160°. For example, contact angles may be achieved from 2° to145°, preferably from 7° to 140°, more preferably from 29° to 133°,especially from 34° to 127°, particularly from 44° to 110°, even morepreferably from 48° to 100°, most preferably from 58° to 86°.

Accordingly, the use of the composition described above for controllingthe wettability of a substrate is a further aspect of the presentinvention, as well as the use of the composition according to theinvention in a coating formulation.

As a result, coatings may be tailor-made as to different wetting,dewetting, drop coalescence and other fluid interaction properties beinguseful in many applications such as protective coatings for packaging(paper, board, plastics, foil), wall-paper, wood, wood composites suchas flake board, plastics, foil, concrete, coated or uncoated rendering,plaster, metals, ceramics, stone, brickstone, glass, etc.

Accordingly, a material comprising the above described composition is afinal aspect of the invention, e.g. a material, which is selected fromthe group comprising paper, board, wall-paper, wood, wood compositessuch as flake board, plastics, foil, concrete, coated or uncoatedrendering, plaster, metals, ceramics, stone, brickstone, glass, etc.

The following figures, examples and tests will illustrate the presentinvention, but are not intended to limit the invention in any way.

DESCRIPTION OF THE FIGURES

FIGS. 1a and 1 b show SEM images of hedgehog shaped PCC particles to beused in the invention.

FIGS. 2a and 2b show SEM images of hedgehog shaped PCC particles to beused in the invention.

FIGS. 3a and 3b show SEM images of hedgehog shaped PCC particles to beused in the invention.

FIG. 4 shows contact angles of substrates coated with different samplesof pre-hydrophobized and/or pre-hydrophilized hedgehog shaped particlesaccording to the invention.

FIG. 5 shows a photograph of a droplet on a substrate being coated witha coating formulation according to the invention having a high contactangle.

FIG. 6 shows contact angles of substrates coated with different samplesof highly coated pre-hydrophobized and/or pre-hydrophilized hedgehogshaped particles according to the invention, as well as additionalhydrophilizing agents.

FIG. 7 shows contact angles of substrates coated with different samplesof slightly coated pre-hydrophobized and/or pre-hydrophilized hedgehogshaped particles according to the invention, as well as additionalhydrophilizing agents.

FIG. 8 shows contact angles of substrates coated with different samplesof pre-hydrophilized hedgehog shaped particles and different binders.

FIG. 9 shows a photograph of a droplet on a substrate having been coatedwith a coating formulation according to the invention having a lowcontact angle.

FIG. 10 shows contact angles of substrates coated with different samplesof pre-hydrophobized and pre-hydrophilized hedgehog shaped particlesaccording to the invention, as well as additional hydrophilizing agentsand binders.

FIG. 11 shows contact angles of substrates coated with different samplesof pre-hydrophobized hedgehog shaped particles in combination withsilicone post-layers.

FIG. 12 shows a photograph illustrating the wetting behaviour ofsubstrates coated with pre-hydrophilized hedgehog shaped particles.

FIG. 13 shows a photograph illustrating the wetting behaviour ofsubstrates coated with pre-hydrophobized hedgehog shaped particles.

FIG. 14 shows a photograph illustrating the wetting behaviour ofsubstrates coated with pre-hydrophobized hedgehog shaped particles andtwo silicone post-layers.

FIG. 15 shows a photograph illustrating the wetting behaviour ofsubstrates coated with pre-hydrophobized hedgehog shaped particles andthree silicone post-layers.

FIG. 16 shows contact angles of substrates coated with different samplesof pre-hydrophobized hedgehog shaped particles using differenthydrophobizing agents, and post-layers of hydrophobizing agents.

FIG. 17 shows contact angles of substrates coated with different coatingformulations and post-layers according to the invention

EXAMPLES

The following experiments were carried out for determining theproperties of compositions according to the invention on the wetting ofsubstrates. This is achieved by preparing coating formulations, applyingthe same on substrates, wetting the substrate surface, and subsequentmeasurement of the contact angles of the water droplets present on thesubstrate surface, wherein the contact angle is an indicator forhydrophobicity/hydrophilicity of a surface.

For this purpose, coating formulations of pre-hydrophobized,pre-hydrophilized and untreated hedgehog shaped PCCs as well as mixturesthereof were prepared, optionally comprising further components.

These coating formulations were applied to Synteape® foils and rawpaper, and, after drying, and, in some cases, application of post-layersof hydrophobizing agent and other agents, the contact angle and/orwetting behaviour was determined.

Example 1: Pre-Treated Hedgehog Shaped Particles 1. Material 1.1.Laboratory Equipment and Methods of Measurement For Coating theSubstrates:

-   -   Erichsen Bar Coater K-Control-Coater K202, Model 624/Fabr. No.        57097-4/wire-wound rod No. 1//Belt dryer 7.0 mmin⁻¹/150° C.

Viscosity Measurement

All Brookfield-viscosities are measured with a Brookfield DV-IIViscometer equipped with a LV-3 spindle at a speed of 100 rpm and roomtemperature (20±3° C.).

Solids Content of an Aqueous Slurry

All mineral preparation solids content (also known as “dry weight”) wasmeasured using a Mettler Toledo HB 43-S Moisture Analyser.

For SEM Images: RDS-ARM-MIC Lims: 220017

Scanning electron micrographs (SEM) were carried out by adjusting thesolids content to a concentration of 20 wt % in water using anultraturax (rotor-stator-mixer). A few drops (approximately 100 mg) werediluted in 250 ml distilled water and filtered through 0.2 μm poremembrane filter. Preparations obtained on the membrane filter in thisway were sputtered with gold and evaluated in the SEM at variousenlargements.

Regarding the SEM images of coatings, a sample of the coated substratewas sputtered with gold and evaluated in the SEM at variousenlargements.

For Contact Angle Measurements:

For measuring the contact angle, 4 water drops of 5 μl each were appliedon 4 Synteape® foils, a photograph was taken 120 s after application.The determination of the contact angle was carried out visually with theaid of the measuring module of the Image Access database Version 8 basedon the photos made of the droplets, and an average value was calculated.

-   Camera: Canon EOS 5D Mark II-   Objective: Canon EF 100 mm f/2 8L Macro IS USMDDDD-   Difference adjustment: 0.3 m-   Distance rings: Kenko distance rings 12+24+36 mm-   Tripod and illumination Kaiser microdrive tripod+2× Repro    illumination equipment RB5055 HF-   Release: Canon remote control/Timer TC-80N3-   Data of recording:-   Brightness balance: automatically-   Lens opening: lens opening adjustment 32-   Illumination time: automatically-   Release delay: 120 s after drop application-   Drop size: 5 μl

1.2. Raw Material

-   -   PCC 1: precipitated calcium carbonate; solids content 18 wt %;        BET specific surface area: 2 m²/g, d₅₀: 8 μm; calcite        content >99%, the crystals having a clustered scalenohedral        morphology (cf. FIGS. 1a and b )    -   PCC 2: precipitated calcium carbonate; solids content 14 wt %;        BET specific surface area: 11.7 m²/g (cf. FIGS. 2a and 2b )

PCC 2 was prepared as follows:

a) Stage 1: Seed Preparation

160 kg of quicklime CaO (e.g., the quicklime supplied by MississippiLime Co., Ste. Geneviève, Mo) was slaked by adding the compound to 1.300litres of 50° C. tap water in a stirred reactor. The quicklime wasslaked for 30 minutes under continuous stirring and the resulting slurryof calcium hydroxide (“milk of lime”) was adjusted to 13% solids contentvia dilution with 60° C. water and was then screened on a 100 μm screen.Prior to the carbonation, 5.0 wt % percent of Sr(OH)₂.8H₂O (based on thedry weight of calcium hydroxide) was added to the milk of lime.

The aragonitic PCC seed precipitation was conducted in a 1 000 litrebaffled cylindrical stainless steel reactor equipped with an gassingagitator, a stainless steel carbonation tube to direct a carbondioxide/air gas stream to the impeller and probes for monitoring the pHand conductivity of the suspension. 800 litres of the calcium hydroxidesuspension obtained in the slaking step above, adjusted to a temperatureof 60° C., were added to the carbonating reactor. A gas of 6% by volumeof CO₂ in air was then bubbled upwards through the slurry at a rate of100 m³/h for 15 minutes (calculated from start of introduction of theCO₂ gas) under a slurry agitation of 1 480 rpm. Thereafter, the CO₂volume fraction in the gas was augmented to 24% and the gas flow ratewas augmented to 200 m³/h. The CO₂ volume fraction and gas flow ratewere maintained at this rate until the end of the reaction. During thecarbonation, the temperature of the reaction mix was not controlled andwas allowed to rise due to the heat generated in the exothermicprecipitation reaction. After conductivity reached a minimumcorresponding to the total conversion of Ca(OH)₂ into PCC, the gassingwas continued for another 8 minutes before the introduction of gas wasstopped. Carbonation time, calculated from start of gas introduction tothe time of minimum conductivity, was 84 minutes. The aragonitic PCCseed slurry was then screened on a 45 μm screen and the screened productwas recovered as an aqueous slurry of the aragonitic PCC seed. Thearagonitic seed carbonation with the addition of 5.0 wt % Sr(OH)₂.8H₂Oyielded an aragonitic PCC seed slurry having 96.1% aragonite.

The aragonitic PCC seed slurry was submitted to post processing bydewatering and grinding it to yield particles having an SSA of 20.6 m²/gand a weight median diameter of 0.22 μm.

b) Stage 2: Manufacturing of Final Aragonitic PCC2

Slaking and carbonation were performed in the same manner as describedabove in Stage 1, except that no Sr(OH)₂.8H₂O was added and 2.5% weightpercent (calculated as dry calcium carbonate based on dry weight ofcalcium hydroxide) of the ground aragonitic PCC seeds formed in Stage 1was added to the milk of lime prior to carbonation. Testing conducted onthe final aragonitic PCC product indicated that 77.6 wt % of the productwas of the aragonitic crystal form. In addition, post processing wasconducted, as described in Stage 1 above, to yield particles having anSSA of 11.7 m²/g and a median diameter of 0.41 μm. Subsequently, anaqueous slurry was prepared having a solids content of 14 wt %. Thehedgehog particle form of PCC2 can be perfectly seen in FIGS. 2a and 2b.

Hydrophobizing Agents:

-   -   Blend of palmitic acid and stearic acid (weight ratio: 1:1) (30        wt % in 95% ethanol): 0.4 g/100 g (0.4 pph) (slightly coated)        and 1.9 g/100 g (1.9 pph) (highly coated) based on the weight of        PCC        Hydrophilizing agents:    -   Polymer solution of 0.33 wt % partially neutralized polyacrylic        acid with a mass weight of 12 000 g/mol and a polydispersity D        (Mw/Mn) of about 3, wherein about 50 mole % of the carboxylic        groups are neutralized with Na⁺ ions; and 0.17 wt % NaH₂PO₄; 0.5        g/100 g (0.5 pph) based on the weight of PCC    -   K4-HEDP (potassium salt of hydroxy ethane-1,1-diphosphonic        acid); solids content 55 wt %; prepared under stirring by adding        potassium hydroxide to HEDP until a pH of 12 is reached:    -   Potassium hyroxide (SIGMA-Aldrich Art. No.: 60370)    -   HEDP (hydroxy ethane-1,1-diphosphonic acid; solids content 60 wt        %, CF Budenheim; trade name Budex 5120)    -   Al(OH)₃-HEDP (aluminium hydroxide/hydroxy        ethane-1,1-diphosphonic acid chelate; weight ratio 1:5); solids        content 53 wt %; prepared under stirring by adding aluminium        hydroxide to HEDP in a weight ratio of 1:5 at room temperature        until a homogeneous mixture is obtained; subsequently heating to        up to 90° C. for 1 h until chelate solution is obtained)    -   Al(OH)₃, Martinswerk (ALBEMARLE corporation), MARTIFIN OL-107    -   HEDP (hydroxy ethane-1,1-diphosphonic acid; solids content 60 wt        %, CF Budenheim; trade name Budex 5120)

Binders

-   -   Acronal® S360D (styrene-acrylic latex); solids content 50 wt %,        BASF Art.: 50005 562    -   Hycar 1562X117 Emulsion (medium acrylonitril; polar latex);        solids content 41.4 wt %, Emerald Performance Materials    -   PVA BF 05 (Polyvinylalcohol) Chang Chun Petrochemicals Taiwan        diluted in cooking water and cooled down, solids content 18 wt %    -   Linseed oil, Aldrich Art. Nr. 430021-250 ML

Post-Layer Treating Agents

-   -   GE Bayer Release Agent M: (siliconizing agent)    -   Stearic acid solution (saturated in 95% ethanol at room        temperature (20±3° C.).

Substrate:

-   -   YUPO (Synteape®)/Art.: 675227, white half-matt PP 18×26 (468        cm²); 62 g/m²    -   Raw paper: Sappi Magno matt classic 18×26 (468 cm²) 82 g/m²

2. Methods 2.1. Sample Preparation 2.1.1 Pre-Treated HydrophobizedParticles

4 000 g of the respective PCC slurries were heated up to 80° C. and ablend of palmitic acid and stearic acid (weight ratio: 1:1) diluted inwarm 95% ethanol (about 50° C.) was added during 10 minutes. The mixturewas stirred for 1 h at 80° C. in a 5 litre double wall steel vesselfitted with viscojet stirrer and thermostat for temperature control.After cooling down, the slurries were dried in an oven for 15 h at 120°C.

2.1.2. Pre-Treated Hydrophilized Particles

To 8 000 g of the respective PCC slurries 0.5 pph of the afore-mentionedpolymer solution of partially neutralized polyacrylic acid were addedduring 10 minutes. The mixture was stirred for 1 h at room temperaturein a 10 litre plastic bucket. The slurries were dried in an oven for 15h at 120° C.

2.1.3. Coating formulations

The coating formulations were produced by adding the pre-hydrophobizedand/or pre-hydrophilized PCC particles in portions, as well asoptionally further components such as further hydrophilizing agents (asindicated below) to a mixture (ideally a solution) of the respectivebinder in tap water under stirring in a VMA Dispermat® (VMA-GetzmannGmbH, Reichshof, Germany) with a 70 mm dispersing disk, and subsequentlystirring the mixture for 1 hour. The coating formulations were screenedover a small tea-sieve having a screen size of 500 μm, and viscosity andsolids content were determined (cf. tables 1 to 5)

All coating formulations showed thixotropic and settling properties. Allcoating formulations containing hydrophobic particles showedanti-wetting properties.

The coating formulations were coated on an impermeable plastic substrate(Synteape®) (two papers per colour) and raw paper for samples 20 (raw)and 21 (raw). On the Synteape® foils, the formulations were applied,pre-dried 3 times under a 150° C. heater via a rolling conveyor belt andpost dried 24 h at room temperature. The resulting film thickness wasfrom 0.1 to 0.3 mg/cm².

2.1.4. Post-Layer

For verifying the impact of post-layering, sample 1 was post-treated byapplying silicone post-layer on top of the PCC coating after drying.This was carried out by means of a commercial spray agent by applyingfor 3 seconds the spray mist onto the coated composition surface. Thus,1 (sample 22S1), 2 (sample 22S2), and 3 (sample 22S3) siliconepost-layers, respectively, were formed on top of the PCC coating.

TABLE 1 Mixtures of pre-hydrophobized and pre-hydrophilized PCC 1 SampleSample Sample Sample 1 2 3 4 Hydrophobized PCC 1 190.5 g 133.3 g 57.1 g— (dry) (0.4 pph) Hydrophilized PCC 1 — 57.1 g 133.2 g 190.5 g (dry)Acronal S 360 D 19.0 g 19.0 g 19.0 g 19.0 g Tap water 290.5 g 290.5 g290.5 g 290.5 g Total 500.0 g 500.0 g 500.0 g 500.0 g Viscosity 130 102160 152 mPa · s/100 rpm Final solids content, 38.9 37.9 39.6 39.8 wt %

TABLE 2 Mixtures of highly coated pre-hydrophobized andpre-hydrophilized PCC 2, and additional hydrophilizing agents SampleSample Sample Sample 5 6 7 8 Hydrophobized PCC 2 94.1 g 85.8 g 36.8 g —(dry) (1.9 pph) Hydrophilized PCC 2 — 36.8 g 85.8 g 122.5 g (dry)Acronal S 360 D 9.4 g 12.3 g 12.3 g 12.3 g Tap water 294.3 g 362.8 g362.7 g 362.8 g K4-HEDP, 55% 2.0 g 2.2 g 2.2 g 2.2 g Al(OH)3-HEDP, 53%0.2 g 0.2 g 0.2 g 0.2 g Total 400.0 g 500.0 g 500.0 g 500.0 g Viscosity340 170 130 121 mPa · s/100 rpm Final solids content, 24.9 24.9 24.825.3 wt %

TABLE 3 Mixtures of slightly coated pre-hydrophobized and pre-hydrophilized PCC 2, and additional hydrophilizing agents Sample SampleSample Sample 9 10 11 12 Hydrophobized PCC 2 151.9 g 86.0 g 36.9 g —(dry) (0.4 pph) Hydrophilized PCC 2 — 36.9 g 86.0 g 122.9 g (dry)Acronal S 360 D 15.2 g 12.3 g 12.3 g 12.3 g Tap water 561.1 g 363.0 g363.0 g 363.0 g K4-HEDP, 55% 1.6 g 1.6 g 1.6 g 1.6 g Al(OH)₃-HEDP, 53%0.2 g 0.2 g 0.2 g 0.2 g Total 730.0 g 500.0 g 500.0 g 500.0 g Viscosity11 130 130 127 mPa · s/100 rpm Final solids content, 21.9 26.0 26.0 26.0wt %

TABLE 4 Different binders used with pre-hydrophilized PCC1 Sample SampleSample Sample 13 14 15 16 Hydrophilized PCC 1 152.0 g 145.5 g 142.9 g136.5 g (dry) Hycar, 41.4 wt % 18.4 g 35.1 g — — PVA, 15 wt % — — 49.3 g94.1 g Tap water 249.6 g 319.4 g 182.9 g 164.4 g Total 420.0 g 500.0 g275.0 g 395.0 g Viscosity 177 177 719 388 mPa · s/100 rpm Final solidscontent, 37.4 31.4 39.5 38.1 wt %

TABLE 5 Different PCCs in the presence of further hydrophilizing agentsSample Sample Sample Sample Sample 17 18 19 20 21 Hydrophilized 73.5 g —— — — PCC 1 (dry) Hydrophobized — — — — 10.0 g PCC 1 (dry) Hydrophobized— 10.4 g 10.4 g 10.0 g — PCC 2 (dry) (1.9 pph) Acronal S 360 D — — — — —Linseed oil — — — 20.0 g 20.0 g K4-HEDP 1.3 g — — — — Al(OH)₃-HEDP 0.1 g— — — — PVA, 18 wt % 20.1 g 69.6 g 69.6 g — — Tap water 205.0 g — 120.0g — — Total 300.0 g 80.0 g 200.0 g 30.0 g 30.0 g Viscosity 102 mPa ·s/100 rpm Final solids 25.2 24.1 10.6 content, wt %

2.2. Determination of the Contact Angle

For determining the contact angle, water drops of 5 μl each were appliedon the coated Synteape® foils. The drops thus formed were photographedand the contact angle was determined with the aid of the measuringmodule of the Image Access database Image Access Version 8. The belowlisted contact angles are an average of several measurements of the samesetup.

TABLE 6 Coated sheets and wetting contact angles Coating/ Coating/Coating/ Coating/ Weight ratio Average sheet sheet sheet sheetHydrophob./ contact Std. (sheet 1) (sheet 1) (sheet 2) (sheet 2)Hydrophil. angle deviation Sample [mg] [mg/cm²] [mg] [mg/cm²] PCC [°][°]  1 148.8 0.3 115.6 0.3 100:0 139 9  2 129.8 0.3 110.7 0.3  70:30 1124  3 133.4 0.3 163.2 0.3  30:70 107 10  4 140.2 0.3 86.8 0.2   0:100 1022  5 59.8 0.2 49.2 0.2 100:0 100 4  6 45.9 0.2 37.5 0.2  70:30 67 3  750.3 0.2 51.3 0.2  30:70 61 9  8 56.8 0.2 51.4 0.2   0:100 44 8  9 38.60.1 42.7 0.2 100:0 102 2 10 50.7 0.1 55.7 0.2  70:30 58 9 11 62.5 0.260.0 0.2  30:70 44 9 12 66.0 0.2 54.3 0.2   0:100 29 7 13 70.5 0.3 84.60.3   0:100 86 2 14 85.5 0.3 72.8 0.3   0:100 81 4 15 115.8 0.3 105.10.3   0:100 48 11 16 134.2 0.3 113.4 0.3   0:100 30 8 17 205.3 0.7 197.00.7   0:100 7 1 18 300.5 0.8 332.5 0.8 100:0 46 3 19 158.2 0.5 157.6 0.5100:0 34 3 20 472.5 1.5 405.5 1.3 100:0 88 2 20 raw — — — — 100:0 110 321 — — — — 100:0 85 2 21 raw — — — — 100:0 103 3 22S1 — — — — 100:0 1322 22S2 — — — — 100:0 133 5 22S3 — — — — 100:0 130 4

As can be taken from the above contact angles, it is possible to controlaccurately the hydrophobicity/hydrophilicity of substrate surfaces bytailor-made coatings using hedge-hog shaped PCC according to theinvention.

As can be seen from samples 1 to 4, the contact angle, and thus thehydrophobicity of the substrate surface can be accurately adjusted bymixing hydrophobized and hydrophilized hedgehog shaped PCC (cf. FIG. 4).

The high contact angle of sample 1 is illustrated by FIG. 5.

The same applies to samples 5 to 8 using a slightly different particleform. Also, in these tests, the contact angle, and thus thehydrophobicity of the substrate surface can be accurately adjusted bymixing hydrophobized and hydrophilized hedgehog shaped PCC. Furthermore,as can be taken from these samples, by admixing further hydrophilizingagents, it is possible to lower the hydrophobicity as desired reflectedby lower contact angles (cf. FIG. 6)

As can be taken from the results of samples 9 to 12, being essentiallyidentical with samples 5 to 8 apart from the fact that the hydrophobizedPCC comprises less hydrophobizing agent, the effects can already beobserved at a rather low amount of hydrophobizing agent (cf. FIG. 7)

In samples 13 to 16, the influence of different binders was evaluated,and it was found that also by using different binders the hydrophilicproperties can be further controlled. Thus, with the same kind ofhydrophilized PCC, hydrophilicity can be increased by using Hycarinstead of Acronal, and can be even more increased by using PVA (cf.FIG. 8)

As can be taken from the results of sample 17, this effect can even beincreased by adding further hydrophilizing agents leading to a nearlycomplete wetting of the substrate surface. The low contact angle ofsample 17 is illustrated by FIG. 9.

The influence of different binders on hydrophobized PCC can be takenfrom the results of samples 18 to 21. Thus, PVA decreases hydrophobicitycompared with Acronal, wherein the effect is dependent on the amount ofwater in the coating formulation. In this respect, it was also shownthat the control of hydrophobicity is not only possible with aqueousformulations, but also in oil-based formulations such as those based onlinseed oil (cf. samples 20 and 21) providing comparable effects (cf.FIG. 10).

Furthermore, looking at the contact angles of samples 20 and 21 onSynteape® foil and raw paper, it can be seen that a higher contactangle, i.e. increased hydrophobicity can be obtained on raw paper.

In samples 22S1, 22S2, 22S3, the influence of a silicone post-layer wasverified. For this purpose a coating of sample 1 was one to three timescoated with silicone post-layers. The results show that the highhydrophobization degree of sample 1 is essentially equal with thesiliconized samples (cf. FIG. 11)

2.3. Wetting

For investigating the wetting behaviour, especially the wettingbehaviour with finely divided water droplets simulating mist or dew,sheets coated with samples 1, 12, 22S2 and 22S3 were mounted on a metalpanel. Deionized water was applied by a micro diffuser. After eachstroke a picture of the sheet was made and the weight of the applieddeionized water was measured. From table 7, the amounts of applieddeionized water can be taken.

TABLE 7 Sample Sample Sample Sample 1 12 22S2 22S3 Stroke No. [g] [g][g] [g] 0 0.000 0.000 0.000 0.000 1 0.327 0.375 0.256 0.483 2 0.7560.807 0.668 0.889 3 1.253 1.143 1.185 1.240 4 1.783 1.467 1.643 1.759 52.277 1.758 2.022 2.152 6 2.753 2.110 2.520 2.623 7 3.546 2.480 3.0643.090 8 3.528 2.796 3.599 3.555 9 3.970 3.120 4.359 4.005 10 4.411 3.4214.941 4.516 11 4.797 3.685 5.491 4.956 12 5.271 3.950 6.022 5.468 135.767 4.209 6.556 5.983 14 6.178 4.607 7.044 6.492 15 6.677 5.039 7.5776.959 16 7.129 5.461 8.006 7.393 17 7.639 5.944 8.422 7.920 18 7.9926.355 8.859 8.363 19 8.366 6.799 9.325 8.879 20 8.740 7.200 9.828 9.32321 9.129 7.701 10.253 9.874 22 9.466 8.149 10.731 10.366 23 9.870 8.63611.185 10.970 24 10.143 9.275 11.609 11.529 25 10.542 9.776 12.09011.987

From the images shown in FIGS. 12 to 15 clearly the wetting(superwetting) behaviour of hydrophilized PCC sample 12 promoting a filmwetting and disabling drop formation can be seen compared to samples 1,22S2 and 22S3, showing repellent/superhydrophobic behaviour promotingdrop formation and drop roll-off, wherein any one of these samples weresprayed with the same amount of water of about 5 g as can be taken fromtable 7 (bold amounts reflect the samples illustrated by FIGS. 12 to15).

Example 2: Untreated Hedgehog Shaped Particles

In Example 2, instead of pre-hydrophobizing/pre-hydropilizing thehedgehog shaped particles, the untreated particles were combined withthe corresponding hydrophilizing and/or hydrophobizing agents uponpreparation of the coating formulation only, and/or by ways of one orseveral post-layers.

1. Material 1.1. Laboratory Equipment and Measurement Methods ForCoating the Substrates:

-   -   Erichsen Bar Coater K-Control-Coater K202, Model 624/Fabr. No.        57097-4/coating rods 1-5 (control of the liquid flow)//Belt        dryer 7.0 mmin⁻¹/150° C.

Spraying

Eco Spray Microdiffusor, Labo Chimie

Solids Content of an Aqueous Slurry

All mineral preparation solids contents (also known as “dry weight”)were measured using a Mettler Toledo HB 43-S Moisture Analyser.

For SEM images:

-   -   RDS-ARM-MIC Lims: 220017    -   Scanning electron micrographs (SEM) were carried out by        adjusting the solids content to a concentration of 20 wt % in        water using an ultraturax (rotor-stator-mixer). A few drops        (approximately 100 mg) were diluted in 250 ml distilled water        and filtered through 0.2 μm pore membrane filter. Preparations        obtained on the membrane filter in this way were sputtered with        gold and evaluated in the SEM at various enlargements.

For Contact Angle Measurements:

-   Camera: Canon EOS 5D Mark II-   Objective: Canon EF 100 mm f/2 8L Macro IS USMDDDD-   Difference adjustment: 0.3 m-   Distance rings: Kenko distance rings 12+24+36 mm-   Tripod and illumination Kaiser microdrive tripod+2× Repro    illumination equipment RB5055 HF-   Release: Canon remote control/Timer TC-80N3-   Data of recording:-   Brightness balance: automatically-   Lens opening: lens opening adjustment 32-   Illumination time: automatically-   Release delay: 120 s after drop application-   Drop size: 5 μl

1.2. Raw Material

-   -   PCC 2: precipitated calcium carbonate; solids content 14 wt %;        BET specific surface area: 11.7 m²/g; prepared as described        above (cf. FIGS. 2a and 2b )    -   PCC 3: precipitated calcium carbonate Omya Syncarb® (available        from Omya AG, Switzerland); solids content: 14 wt %; BET        specific surface area: 3.5-6.5 m²/g (cf. FIGS. 3a and 3b )

Hydrophobizing Agents:

-   -   ASA Nalsize 7541 (Alkyl succinic anhydride); solids content        22.29 wt %, Ondeo Nalco Co.    -   AKD DR28XL (alkylketene dimer); solids content 23.9 wt %, Eka        Chemicals    -   Stearic acid, Sigma S4751-100G    -   Wükoseal® 805; solids content 40 wt %; Süddeutsche        Emulsions-Chemie GmbH (SEC), Mannheim-Neckarau, Germany    -   Silres BS 1306 (polysiloxane modified with functional silicone        resin), solids content 55 wt %; Wacker Chemie AG

Binders

-   -   Acronal® S360D (styrene-acrylic latex) solids content 50 wt %,        BASF Art.: 50005 562

Substrate:

-   -   YUPO (Synteape®)/Art.: 675227, white half-matt PP 18×26 (468        cm²); 62 g/m²

2. Methods 2.1. Sample Preparation

With the below samples given in tables 8 and 9, several embodiments ofthe invention were verified:

a) Samples 23 to 26 (PCC2) and 28 to 29 (PCC3): Combination of hedgehogshaped particles with the binder and the hydrophobizing agent in orderto obtain a corresponding coating formulationb) Samples 26 SA1 (PCC2), 26 SA2 (PCC2), 28 SA (PCC3) and 29 SA (PCC3):Combination of sample 26 comprising hedgehog shaped particles, binderand hydrophobizing agent with additional hydrophobizing agent in theform of one to two post-layers of stearic acid after having coated itonto the substrate.c) Samples 27 SA (PCC3): Combination of hedgehog shaped particles andbinder, whereas the hydrophobizing agent is combined with this mixturein the form of a post-layer of stearic acid after having coated it ontothe substrate.

TABLE 8 Sample Sample Sample Sample 23 24 25 26 PCC 2 (dry) 238.5 g242.1 g 249.6 g 236.0 g Acronal S360D 6.9 g 7.0 g 7.0 g 6.8 g AKD Eka DR28 XL 5.8 g — — 5.7 g Wükoseal 805 — 0.9 g — 0.9 g Silres BS 1306 — —0.6 g 0.6 g Tap water 148.8 g 150.0 g 211.8 g 150.0 g Total weight 400.0g 300.0 g 460.0 g 400.0 g Final solids content, 18.5 18..0 15.7 18.8 wt%

TABLE 9 Sample Sample Sample Material 27 28 29 PCC 3 (dry) 82.8 g 82.2 g44.3 g Acronal S360D 3.1 g 3.1 g 1.7 g AKD Eka DR 28 XL — 2.6 g — ASANalsize — — 1.5 g Tap water 14.1 g 12.1 g 2.5 g Total weight 100.0 g100.0 g 100.0 g Final solids content, 33.2 wt % 33.6 wt % 36.2 wt % wt %

The coating formulations were prepared by adding PCC2 or PCC3,respectively, as well as the hydrophobizing agents (if present), inportions, to a mixture (ideally a solution) of the respective binder intap water under stirring in a VMA Dispermat® (VMA-Getzmann GmbH,Reichshof, Germany) with a 70 mm dispersing disk, and subsequentlystirring the mixture for 1 hour. The coating formulations were screenedover a small tea-sieve having a screen size of 500 μm, and the solidscontent was determined (cf. tables 8 and 9). Subsequently, the solidscontent was adjusted by adding further water.

The resulting coating formulations were coated onto an impermeableplastic substrate (Synteape®) with coating rods 1-3. Two papers werecoated per colour and coating rod.

Drying circles were carried out in a belt dryer at 150° C. with a bandspeed of 6-7 until the colour is dry.

The Synteape® papers coated with samples 26, 27, 28 and 29 wereadditionally sprayed with a solution of 2.8 g stearic acid in 46.0 gethanol (6 wt % solution) into a small fume hood. The solution wasprepared by heating the ethanol to 50° C. in a water bath. After thesolvent had reached the temperature, the stearic acid was addedmanually, mixed by rotation in a round bottomed flask and then sprayeddirectly on the surface of the coated papers.

In the case of samples 26SA1 and 26 SA2 one or two spray cycles,respectively, were carried out to obtain a good coating layer (cf. table11). In the case of samples 27 to 29 the coated sheets were sprayeduntil the layer weight given in table 12 was obtained.

2.2. Determination of the Contact Angle

For determining the contact angle, the coated sheets were wetted bydropping 5 μl deionized water during 120 s onto the sheet surface. Thedrop thus formed was photographed and the contact angle was determinedwith the aid of the measuring module of the Image Access database ImageAccess Version 8.

TABLE 11 Coating weights Average Average Average coating/ coating/Contact Std. sheet sheet angle deviation Trial [mg] [mg/cm²] [°] [°]Sample 23 265.0 0.1 128 5 Sample 24 321.0 0.1 132 2 Sample 25 200.5 0.1124 3 Sample 26 313.5 0.1 144 5 Sample 26SA2 313.5 0.1 140 3 Sample26SA2 313.5 0.1 131 6

TABLE 12 Coating and Post-layer weights Average Average Average AverageAverage coating/ coating/ postlayer/ postlayer/ Contact Std. sheet sheetsheet sheet angle deviation Trial [mg] [mg/cm²] [mg] [mg/cm²] [°] [°]Sample 27SA 34.7 0.1 149.7 0.3 139.8 9.5 Sample 28 140.3 0.3 — — 130.93.0 Sample 28SA 140.3 0.3 149.2 0.3 144.9 8.1 Sample 29 105.6 0.2 — —103.2 12.1 Sample 29SA 105.6 0.2 148.8 0.3 122.7 12.5

From FIG. 16, the influence of untreated PCC 2 combined with differenthydrophobizing agents and binder upon preparation of a coatingformulation is illustrated by the contact angles of samples 23 to 26,wherein any one of the samples provide a good hydrophobicity reflectedby contact angles of around 124 to 132°. The hydrophobization can evenbe increased by a combination of the hydrophobizing agents as reflectedby sample 26 providing a contact angle of 144°.

Furthermore, several tests were made with respect to a furtherhydrophobization of sample 26 by post-layering with stearic acid. As canbe seen from FIG. 16, this treatment resulted in a decrease of thehydrophobization.

The contact angle of sample 27 exemplifying hydrophobization bypost-layering only, illustrates that a high hydrophobization degree canalso be achieved by post-layering.

Finally, the contact angles of samples 28 and 29 show the influence ofdifferent hydrophobizing agents combined with untreated PCC and binderupon preparation of a coating formulation, wherein the hydrophobizationin both cases can be increased by post-layering as exemplified bysamples 28SA and 29SA (cf. FIG. 17).

1. A composition comprising: a) hedgehog shaped particles composed of acalcium carbonate containing material, b) at least one binder, and c)(i) at least one hydrophilizing agent, or (ii) at least onehydrophobizing agent and at least one hydrophilizing agent, wherein thehedgehop shaped particles: (i) are pre-treated with the at least onehydrophilizing agent and then combined with the at least one binder, or(ii) are pre-treated with the at least one hydrophobizing agent and thencombined with the at least one binder and the at least onehydrophilizing agent.
 2. The composition according to claim 1, whereinthe hedgehog shaped particles are composed of aragonitic precipitatedcalcium carbonate in a form of clusters of needle like crystals.
 3. Thecomposition according to claim 1, wherein the hedgehog shaped particlesare clusters and/or aggregates of scalenohedral precipitated calciumcarbonate.
 4. The composition according to claim 1, wherein the hedgehogshaped particles have a BET specific surface area of from 1 to 50 m²/g,measured using nitrogen and the BET method according to ISO
 9277. 5. Thecomposition according to claim 1, wherein the hedgehog shaped particleshave a BET specific surface area of from 2 to 40 m²/g, measured usingnitrogen and the BET method according to ISO
 9277. 6. The compositionaccording to claim 1, wherein the hedgehog shaped particles have a BETspecific surface area of from 11 to 35 m²/g, measured using nitrogen andthe BET method according to ISO
 9277. 7. The composition according toclaim 1, wherein the hedgehog shaped particles have a BET specificsurface area of from 15 to 20 m²/g, measured using nitrogen and the BETmethod according to ISO
 9277. 8. The composition according to claim 1,wherein the hedgehog shaped particles have a weight median particlediameter d₅₀ of from 1 μm to 50 μm.
 9. The composition according toclaim 1, wherein the hedgehog shaped particles have a weight medianparticle diameter d₅₀ of from 2 μm to 40 μm.
 10. The compositionaccording to claim 1, wherein the hedgehog shaped particles have aweight median particle diameter d₅₀ of from 3 μm to 30 μm.
 11. Thecomposition according to claim 1, wherein the hydrophobizing agent isselected from the group consisting of fatty acids, stearic acid,palmitic acid, and their salts; alkylketene dimer; polyacrylamideresins; silicone resins, polysiloxanes, polysiloxane modified with afunctional silicone resin, and any mixture thereof.
 12. The compositionaccording to claim 1, wherein the hydrophilizing agent is selected fromthe group consisting of polyacrylic acids, salts of1-hydroxyethane-1,1-diphosphonic acid, alkali metal salts thereof,potassium salts thereof; chelates of 1-hydroxyethane-1,1-diphosphonicacid, aluminium hydroxide chelates thereof, aluminiumhydroxide/1-hydroxyethane-1,1-diphosphonic acid chelates having a weightratio of 1:5, and any mixture thereof.
 13. The composition according toclaim 1, wherein the at least one hydrophilizing agent, or thehydrophobizing agent and the least one hydrophilizing agent is presentin an amount of from 0.1 to 10 wt %, based on the weight of the hedgehogshaped particles.
 14. The composition according to claim 1, wherein theat least one hydrophilizing agent, or the hydrophobizing agent and theleast one hydrophilizing agent is present in an amount of from 0.2 to 5wt %, based on the weight of the hedgehog shaped particles.
 15. Thecomposition according to claim 1, wherein the at least onehydrophilizing agent, or the hydrophobizing agent and the least onehydrophilizing agent is present in an amount of from 0.3 to 2.4 wt %,based on the weight of the hedgehog shaped particles.
 16. Thecomposition according to claim 1, wherein the at least onehydrophilizing agent, or the hydrophobizing agent and the least onehydrophilizing agent is present in an amount of from 0.4 to 1.9 wt %,based on the weight of the hedgehog shaped particles.
 17. Thecomposition according to claim 1, wherein the at least onehydrophilizing agent, or the hydrophobizing agent and the least onehydrophilizing agent is present in an amount of from 0.5 to 1.5 wt %,based on the weight of the hedgehog shaped particles.
 18. Thecomposition according to claim 1, wherein the binder is selected fromthe group consisting of latex binders, hybrid binder systems;homopolymers or copolymers of acrylic and/or methacrylic acids, itaconicacid; acid esters, ethylacrylate, or butyl acrylate; styrene,unsubstituted or substituted vinyl chloride, vinyl acetate, ethylene,butadiene, acrylamides and acrylonitriles; silicone resins, waterdilutable alkyd resins, acrylic/alkyd resin combinations, polyvinylalcohol, natural oils, linseed oil, and any mixture thereof.
 19. Thecomposition according to claim 1, wherein the binder is present in anamount of up to 250 wt %, based on the weight of the hedgehog shapedparticles.
 20. The composition according to claim 1, wherein the binderis present in an amount of up to 200 wt %, based on the weight of thehedgehog shaped particles.
 21. The composition according to claim 1,wherein the binder is present in an amount of up to 150 wt %, based onthe weight of the hedgehog shaped particles.
 22. The compositionaccording to claim 1, wherein the binder is present in an amount of upto 120 wt %, based on the weight of the hedgehog shaped particles. 23.The composition according to claim 1, wherein the binder is present inan amount of 1 to 50 wt %, based on the weight of the hedgehog shapedparticles.
 24. The composition according to claim 1, wherein the binderis present in an amount of 3 to 25 wt %, based on the weight of thehedgehog shaped particles.
 25. The composition according to claim 1,wherein the binder is present in an amount of 5 to 20 wt %, based on theweight of the hedgehog shaped particles.
 26. The composition accordingto claim 1, wherein the binder is present in an amount of 10 to 15 wt %,based on the weight of the hedgehog shaped particles.
 27. Thecomposition according to claim 1, wherein the hedgehog shaped particlesare pre-treated with the at least one hydrophilizing agent and thencombined with the at least one binder.
 28. The composition according toclaim 1, wherein the hedgehog shaped particles are pre-treated with theat least one hydrophobizing agent and then combined with the at leastone binder and the at least one hydrophilizing agent.
 29. Thecomposition according to claim 1, which is in the form of a solution ordispersion in a liquid medium, or is in the form of a medium selectedfrom the group consisting of water, alcohol ethers, alcohols, aliphatichydrocarbons, esters, and any mixture thereof.
 30. The compositionaccording to claim 29, further comprising additives selected from thegroup consisting of dispersing agents, siliconizing agents, thickeners,rheology modifiers, anti-settling agents, defoamers, antioxidants,bluing agents, surfactants, crosslinkers, flame retardants, catalysts,pH buffers, fillers, dyes, pigments, optical brightners, waxes,coalescence agents, biocides and any mixture thereof.
 31. A coatingformulation comprising the composition according to claim
 1. 32. Amaterial comprising the composition according to claim 1, wherein thematerial is selected from the group consisting of paper, board,wall-paper, wood, wood composites, lake board, plastics, foil, concrete,coated or uncoated rendering, plaster, metals, ceramics, stone,brickstone and glass.